1. Field of the Invention
Embodiments of the invention generally relate to process kit for a semiconductor processing chamber, and more specifically, to a notched deposition ring.
2. Description of the Related Art
In deposition processes, species from a source such as a target, a gas inlet manifold and the like, may deposit on exposed internal chamber surfaces, including chamber walls, substrate pedestal assemblies, electrostatic chucks and other hardware. Process kits, such as shield assemblies, have been developed that circumscribe the electrostatic chuck within a semiconductor processing system to protect the chuck from exposure to the deposition species within the system. One shield assembly includes a removable cover ring and a deposition ring.
The deposition ring rests upon a circumferential flange extending from an outer edge of the electrostatic chuck. The support surface of the chuck, upon which a substrate is retained, has a diameter that is slightly smaller than the diameter of a substrate. Consequently, a substrate retained by the chuck overhangs an inner portion of the top surface of the deposition ring. The cover ring circumscribes and rests upon an outer portion of the deposition ring. The cover ring has a lip that overhangs the outer portion but does not contact a top surface of the deposition ring, thereby defining a labyrinth gap between the cover and deposition rings. The labyrinth gap separating the rings prevents deposition species from passing between the space and into contact with the electrostatic chuck.
Although shield assemblies having the above-described configuration have demonstrated robust performance, improvements are desired that reduce the potential for particular generation within the chamber and/or enhance longer production runs between replacement of the rings for cleaning. For example, deposition build-up on the rings may lead to undesirable electrical bridging between the rings that adversely affect process performance, thereby requiring periodic ring replacement for cleaning. Deposition build-up is particularly problematic below the substrate notch, which exposes the underlying deposition ring to a greater flux of deposition species relative to the surrounding area of the ring.
Therefore, there is a need for an improved process kit.